Electrical apparatus



y 1954 T. TOGNOLA ,6 5

ELECTRICAL APPARATUS Filed June 9. 1949 INVENTOR.

ATTOP/Vfy Patented July 27, 1954 NIT-ED "ties are Ni" wastes ELECTRICAL APPARATUS "Tullio Tognola sidney, N. Y., assignorto Bendix Aviation- Corporation, New York, "N. Y., a corporationiof Delaware -Application June'"9, 1949,:S'erial 'No. 98,093

" Claims. (Cl.'123- -169) 1.1 ,2 f This invention relates .to electrical apparatus Fig.-2 is-a bottom view of the device of 'Fig.1; .andmoreparticularly toidevices adapted for'use Figs. 3 and i are sectional side elevation views in creating electrical spark discharges -between similar to Fig. 1, with part broken}away,-'shows'pa'ced electricalconducto'rs. 'ing other forms of spark gap construction em- One of the objects of the present invention is 5 body-ing the invention; and to,provide apno'vel' sparkgap construction where- "Fig. 5 is a bottom vi-ew of the device of Fig; 4. lby a high-energy spark :discharge maybe'created In the embodiments illustrate'din the draw- .across a relatively wide. gap atrelatively low ing, by wayofexample,-thepresent' inventionis voltage, shown asbeing embodiedin devices known comlinqther'object'ofthe invention isto provide a m 'mercially as spark 'plugs, :said de'vi'ces being novelly constructed sparkiplug "for a combustion adapted for use in igniting-a; combustible-charge engine or the iikefwherebyignition of a-comin the combustion chamber of "an :engine. As l'bust'ible charge'inay be obtained. ShOWn'in Fig. 1, said device comprises atubular A"jfurther object'is to provide a spark plug -metallic shell lil adaptedior threadedengagewhich.willfirelmderadverseconditions far worse 1 ment withan opening in the "cylinder of'aninthantthose' which would 'causenertain failure of 'ternal coinbustionen e ofm he wallbf t e operation inknown types of spark plugs for the combustion chamber of a =j'et type engineer-the samepurpose. like. In jettype engines the threads'on the shell charge device embodying novel means' for in'itiat- Another objectis to provide a spark plugwhi'ch 'may i be replaced by amounting flange 01" other will fire" or spark at very low' voltages'sothat 2O suitable supporting means. -At the lower .or inner the mechanical construction ofthe plugmaybe end of shell Iil'lsan internal flange 'II which greatly simplified without danger of 'failure in forms .a shoulder'tosupportandlposition the inoperation due to flash overs and the-like. ternal ri ass'embly of the plug. Seated on said *still another'objectisto provideafdevi'ce hav- Shoulder and h vin l ri ln a m nt"w th inga 'novel spark gap construction *whichinshell lfiis'a ring electrode l2which may made "herently functions to" prevent anyserious 'foul- "of tungsten, nickel alloy or other suitable elecng f' v a v y' t' ap and h ence"to" p'retrically conductive material. This electrode vent short-circuiting of the gap and consequent preferablylias asliding: fit Withintheboreof shell 'failure of operation. I'D to thereby center the sa-me within theshell. *AStill further object is to providea-spark=dis The e ga ng rfaces 'f' ins "i and ll 1 may be silver soldered or otherwise suitably 'ing-a'spark discharge'from a souree, the voltage joinedtogetherto insure good electrical contact "of which is considerably below the normal 'breakand a high rate of heat dissipation from the down'or'spaik-over voltage of the gap, electrode.

Another'object isto-pr'ovi'de'a novel-'spai'k 'plug The center assembly Withimshell il-c p s "for'combus'tionengines whieh is so constructed as a central metallic rod [4 which may e recessed tosubstaritieilly eliminate an danger "of 'prefi dw h pp r 5- t ersuitable metal "from the following "detail description-when the 1 ing drawings. It is. to be expressly understood.

- m as a result of overheatin fdfithezgspgj-k having high-heat conductivity. 'lhe outer end of "plug "parts exposed tothe combustion chamber islprovidedwvith angxternalfiangellfiathe "of the engine. upper face of which is in approximately the The-above and further objects-andnovel feam plane/as the corresponding-facelof-flange ftures of the invention will more fully appear Seated on flange inner electrode'ring I! which has aslidingfit on-rod ifl-andhasagood electrical contact therewith. Ring 1 mayii desiredpbe secured to rod lfiin the same-mannerthat ring 12 is securecl inthe shell. "-The 'howevel that the drawings Intended to outer diameter oif electrode I 1 is-somewhat less .definejthe limits of the invention refer'eno'effor f .1 than the-innerdiamete n el this-latter purpose bemg had primarily .to;the 1hereby forming an i g 5 g fig' p d l I r -width of which -may vary appreciably, Y either Imthe drawmgs' Wherem'hke reference 60 aboveor below the Width of g'aps foundsa'tis'facsarne'is read in connection with theaccomp'any- .actersiefer to like parts-throughout'theseveral t k types fs afk pluga .Electrode .views, n I ll mayalsobema'd-e of tungsten, nickel alloy or ;-:Fig,&1;1lS a=S8Ct1On3;1-SidO'BlGVQJZlOIlJZIBW showlng other suitable conductive material which has one;.form-. ofedevice-embodying the-present 'invenbeen .-found satisfactory 'for use as' Spark p 'tion; electrodes.

Novel means are provided for inducing an electrical spark discharge across gap It between the adjacent surfaces of electrode rings I2 and H. In the form shown said means is constituted by a high resistance or semi-conductive ring I3 having surface contact with the electrode rings and bridging the gap I8 at the inner edge thereof. Ring i9 thus constitutes a high resistance path between electrodes I1 and I2 which apparently functions in an advantageous manner to be presently more fully described. The materials from which ring I9 is made may be chosen from a variety of suitable substances, the best choice being somewhat dependent upon the ultimate operating conditions. Ring I9 should, it is believed, be so constituted that an initial surge of electrical energy from a discharging condenser or the like at a voltage below the normal spark-over voltage of the gap will flow from electrode I? to electrode I2 along the lower surface or skin of resistor ring I9 adjacent the gap. This electrical action apparently results in the ionization of the medium within gap I3 and reduces its spark-over or break-down voltage to a value not greater than the voltage of the remaining charge on the condenser or other source. With the resistance of the gap thus reduced, the remaining charge stored in the condenser will be dissipated across the gap in the form of a high-energy, low-voltage, highfrequency spark discharge.

It is preferable that ring I9 be insulated from both the center electrode bar It and shell ii! to thereby avoid the passage of excessive current through the body of the ring or along a surface which is not exposed to the gap. To this end, the outer periphery of ring I may be engaged by a depending annular skirt on an insulating spool 2 I, the center part of which completely fills a portion of the bore of shell H3 around rod I to position the latter within the shell. Preferably, skirt or flange 20 does not engage electrode I2 so that ring I9 may contact said electrode under pressure to insure good electrical and heat conductions. An annular skirt 22 at the upper end of insulator 2I serves as a pilot for a cylinder or sleeve 23 of copper or other suitable high heat conducting electrical conductor. Sleeve 23 has an internal shoulder 24 against which the upper end of hollow rod i4 is spun or rolled to form a head 25, whereby said rod, rings I1 and I9, insulator 2 I, and sleeve 23 are rigidly secured together under pressure as a unit or sub-assembly which may be readily inserted into shell If! for engagement with electrode ring I2 as heretofore described.

The above-described central sub-assembly, which is in eifect a center electrode assembly, may be secured in shell I0 by a gland nut 26 which is threadedly received by the upper end of the shell. In order to insulate the electrically conductive parts of the center electrode assembly from the shell and hence from ground, an insulator 2"! is interposed between nut and the upper end of sleeve 23. Said insulator also has a depending skirt 28 for positioning the upper end of sleeve 23 and spacing it from the inner wall of shell If]. The annular space between insulators 2i and 21 around sleeve 23 is preferably filled with a closely packed powdered insulation 29, several kinds of which are available. For example, powdered aluminum oxide, clay, magnesium oxide or the like constitute suitable fillers, but other types of solid or powdered insulation may be employed. A type of filler which will serve to conduct heat from sleeve 23 to shell II] is desirable.

4 Suitable longitudinal pressure may be applied to the center assembly by nut 26 which, when tightened, may be brazed or otherwise suitably locked to shell I0.

Nut 26 is tubular and has a pin or plug contact terminal 3I mounted centrally thereof by means of a well known type of glass-to-metal seal 32. The outer end of said nut is externally threaded and recessed for receiving the female part of a plug and socket connector, in a manher well known in the art, to effect electrical connection between the spark plug and a source of electrical energy (not shown). The inner end of pin 3! extends into and makes electrical contact with a socket 33. The upper or hollow end of the latter comprises a plurality of spring metal prongs which resiliently engage pin 3|, and the lower or solid portion of the socket member has a tight fit in a metal sleeve 34 which in turn has a press fit in the bore of sleeve 23. The void spaces within the spark plug may be filled under vacuum with a suitable insulating compound, if desired, in a manner now well understood in the art.

From the above description it will be understood that electrical energy may be supplied from a high frequency or other source to the spark plug through terminal pin 3I. From pin 3I the current flows through socket member 33, sleeves 34 and 23, and rod I4 to inner electrode ring ll. When voltage is applied, the initial surge of current is believed to flow through resistor I9 along or adjacent to the lower surface or skin of said resistor adjacent gap I8 and thence to ground through outer electrode ring I2 and shell Ill. The gap I8 is thereupon ionized, and the remainder of the stored or available energy creates a spark across gap I8. Successive sparks may occur at different points along the gap and are eifective to burn or drive out of the gap any accumulations of foreign matter which might otherwise foul the gap and create a permanent low resistance path between the gap surfaces, a condition known in the art as fouling.

Some of the materials which may be suggested, by way of example, for use in making semi-conductive ring I 9 comprise various fused or compressed mixtures of suitable insulators, such as sodium silicate, clay, titanium dioxide, zirconium oxide, urea formaldehyde resins, and/or aluminum oxide with finely divided. electrical conductors such as silicon carbide, titanium carbide, nickel, boron carbide, graphite, iron or the like. The insulating materials act as binders in the suggested mixtures for the electrically conductive compound. Ring I9 should be so constituted as to withstand high temperatures and substantial pressures when heated to operating temperature. It must also possess the property of resistance to burning and erosion in the presence of high energy spark discharges acros gap I8. Fused mixtures of silicon carbide, alumina and sodium silicate and of iron powder and alumina have proved quite satisfactory in some installations. It may be desirable to concentrate the conductive materials near the surface of ring I9 adjacent the gap to insure against possible dissipation of the electrical energy through the semi-conductive body rather than along the surface or skin thereof. If the cross-section of the resistor is small, the resistance may be sufliciently high even though a relatively good conductor is employed. The choice of materials and detail structure or composition of the resistor are matters for some experiment in each parannular spark gap between said head portion and the ground electrode.

4. A spark plug as defined in claim 2 wherein the resistor element is detached from the said insulating means and consists of a rigid mixture of finely divided electrically conductive material and insulating material.

5. A spark plug as defined in claim 2 wherein said resistance element has a sliding fit in and projects from a recess in said tubular insulating means.

6. A spark plug as defined in claim 2 wherein the center electrode comprises an electrode ring having at least a marginal portion thereof interposed between said resistance element and said head portion.

7. A spark plug as defined in claim 2 wherein said ground electrode i constituted by a ring mounted in said shell.

8. A spark plug as defined in claim 2 wherein said ground electrode is constituted by a ring mounted in said shell and said center electrode comprises an electrode ring having at least a marginal portion thereof interposed between said resistance element and said head portion in spark gap relation with said ground electrode ring.

9. An ignition spark plug comprising a tubular metallic shell, an annular ground electrode adjacent one end of said shell, a center electrode assembly within the shell comprising a metallic rod with a spindle portion and anenlarged head portion constituting a center electrode and forming an annular spark gap with said ground electrode, means for insulating said rod from said shell and resistor means bodily separate from said insulating means and having a marginal portion tightly clamped between said insulating means and said center electrode and another marginal portion seated on said ground electrode, and means for securing said assembly in said shell and pressing said resistor means against said ground electrode, said resistor means being in spaced re-- lation to both said shell and spindle.

10. A spark plug as defined in claim 9 wherein the resistor is in the form of a ring having appreciable thickness and completely covering the spark gap at the inner edge thereof.

11. A spark plug as defined in claim 10 wherein the resistor ring is positioned by said insulating means in spaced relation to the inner wall of the shell and the external surface of said spindle.

12. A spark plug comprising a tubular shell, an annular ground electrode adjacent one end of said shell, a center electrode assembly adapted to be assembled independently of said shell and ground electrode and insertable within said shell after being assembled, said assembly comprising a metallic rod having a spindle and an enlarged head portion constituting an electrode in spark gap relation with said ground electrode, a resistor bridging the gap between said electrodes and having surface contact with the upper surfaces only of both said electrodes and a tubular insulator surrounding said spindle, said insulator and resistor being rigidly secured to said rod with the resistor in firm engagement with said head portion and in spaced relation to said shell and spindle, and a tubular nut threadedly received by said shell for applying pressure to said assembly to press said resistor against said ground electrode.

13. A spark plug as defined in claim 12 wherein the ground electrode is constituted by a ring mounted in said shell and said center electrode assembly includes an electrode ring having at least a marginal portion thereof interposed between said resistor and said head portion in spark gap relation with said ground electrode ring.

14. A spark plug as defined in claim 12 including a plurality of circumferentially spaced resistors slidably extending into and projecting from recesses in said tubular insulator.

15. In a spark plug, two coplanar fiat annular discs of different dimensions concentrically disposed and having a circular space of substantially uniform cross-section between them to provide a spark gap, electrically conductive supporting means for the smaller disc engaging said disc at its upper, lower and internal surfaces, electrically conductive supporting means for the larger disc engaging said disc at its upper, lower and external surfaces, and an electrically insulative member mechanically interconnecting the two supporting means and retaining them fixedly positioned with respect to each other.

16. A spark plug as in claim 15 in which the discs are of substantially equal thickness and are of different internal and external diameters.

17. A spark plug as in claim 15 in which the supporting means are shaped to provide a circular groove having tapering walls sloping inwardly towards the spark gap, whereby the gases to be ignited by the spark plug may have free access to the spark gap.

18. In a spark plug, two concentric annular discs having an annular space of substantially uniform radial thickness therebetween to provide a spark gap, means for supporting said discs including means engaging the inner disc at its upper, lower and internal surfaces and the outer disc at its upper, lower and external surfaces, said disc-engaging means including an electrically conductive element engaging said inner disc and an electrically conductive element engaging said outer disc, and means including electrically insulative means mechanically interconnecting said disc-supporting elements and retaining said elements in fixed position with respect to each other.

19. In a spark plug, two concentric annular electrodes having an annular space therebetween of substantially uniform radial thickness to provide a spark gap, the innermost of said electrodes comprising an annular disc, electrically conductive supporting means for said disc engaging the same at its upper, lower and internal surfaces, electrically conductive supporting means for the outermost of said electrodes, and means including electrically insulative means mechanically interconnecting the two electrode-supporting means and retaining them in fixed position with respect to each other.

20. In a spark plug, two concentric annular electrodes having an annular space therebetween of substantially uniform radial thickness to provide a spark gap, the innermost of said electrodes comprising an annular disc, electrically conductive supporting means for said disc engaging the same at its upper, lower and internal surfaces, electrically conductive means engaging the outermost of said electrodes at its lower and external surfaces, said last-named means including supporting means for said outermost electrode, and means including electrically insulative'means mechanically interconnecting said electrode supporting means and retaining the same in fixed position with respect to each other.

(References on following page) References Cited. in the file of this patent UNITED STATES PATENTS Number Name Date Smits May 9, 1950 Smits Oct. 24, 1950 Smits Dec. 18, 1951 SmitS Aug. 5, 1952 Number 10 FOREIGN PATENTS Country Date Great Britain Apr. 28, 1939 Great Britain May 15, 1941 France Apr. 7, 1942 France June 23, 1943 France Oct. 15, 1943 

